Integral actuator design

ABSTRACT

An integrated actuator drive unit (ADU) assembly for an electric motor actuator is disclosed. The integrated ADU assembly may comprise at least one of an integrally formed ring gear, an integrally formed thrust bearing and integrally formed load cell. The integrated ADU assembly may comprise a portion of an electromechanical actuator. The electromechanical actuator may be utilized for aircraft braking systems.

FIELD

The present disclosure relates to braking systems and, morespecifically, to a load cell, thrust bearing, and planetary ring gearcomposed integrally as part of an actuator drive unit (ADU) of anelectromechanical actuator (EMA).

BACKGROUND

Typical electric motor actuators in aircraft and/or large vehicle (e.g.,trains, commercial equipment, and/or the like) brake systems may employa load cell that is installed within the actuator housing. When theactuator is engaged, the load cell is loaded in compression.Electromechanical actuators may comprise braking assemblies thatforcefully move a translating member (e.g., such as a “ball nut”)against a brake disk stack to generate an actuation force. This brakingassembly may utilize an actuator. This actuation force drives the ballnut into forceful engagement with the brake disk stack to generate abraking torque. This actuation force loading may be sensed as strainmeasurement (e.g., indirectly) by a load cell.

SUMMARY

An integrated actuator drive unit (“ADU”) assembly for an electric motoractuator is disclosed herein. The integrated ADU assembly may compriseat least one of an integrally formed ring gear, an integrally formedthrust bearing and integrally formed load cell. The integrated ADUassembly may comprise a portion of an electromechanical actuator. Theelectromechanical actuator may be utilized for aircraft braking systems.The electric motor actuator may include an electric motor actuatorhousing, a ball screw coupled to the electric motor actuator housing, aball nut in communication with the ball screw and an actuator drive unithousing coupled to the ball screw to form a thrust bearing.

According to various embodiments, the actuator drive unit may include anADU housing. At least a portion of the exterior surface of the ADUcomprises a thrust bearing race. The actuator drive unit may include anintegrally formed ring gear. Teeth of the ring gear may be formed alongan interior surface of the actuator drive unit housing. The actuatordrive unit may include an integrally formed load cell. The load cell maybe defined by a portion of the actuator drive unit housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIG. 1 illustrates a cross-sectional side view of a prior art electricmotor actuator;

FIG. 2 illustrates a perspective view of an electric motor actuatorhaving an integrated load cell, thrust bearing, and planetary ring gear,in accordance with various embodiments; and

FIG. 3 illustrates a cross-sectional side view of an EMA assembly havinga load cell, thrust bearing, and planetary ring gear composed integrallyas part of an actuator drive unit (ADU), in accordance with variousembodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration and their best mode. While these exemplary embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the inventions, it should be understood that other embodimentsmay be realized and that logical, chemical and mechanical changes may bemade without departing from the spirit and scope of the disclosure.Thus, the detailed description herein is presented for purposes ofillustration only and not of limitation. For example, the steps recitedin any of the method or process descriptions may be executed in anyorder and are not necessarily limited to the order presented.

Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact.

As used herein, phrases such as “make contact with,” “coupled to,”“touch,” “interface with” and “engage” may be used interchangeably.

In various embodiments, an aircraft wheel and brake system may comprisea non-rotatable wheel support, a wheel rotatably mounted to the wheelsupport, and a brake disk stack having alternating rotor and statordisks mounted with respect to the wheel support and wheel for relativeaxial movement. Each rotor disk may be coupled to the wheel for rotationtherewith and each stator disk may be coupled to the wheel supportagainst rotation. A back plate may be located at the rear end of thedisk pack and a brake head may be located at the front end. The brakehead may house a plurality of electric motor actuator (“EMAs”) thatfurther comprise reciprocating rams that extend to compress the brakedisk stack against the back plate. Torque is taken out by the statordisks through a static torque tube or the like. An aircraft brake systemmay include the brake disk stack, the brake head, and at least one EMAmounted to, for example, the brake head. The EMA may include a housing,a reciprocating ram and a motive device operatively connected to thereciprocating ram for selectively moving the reciprocating ram into andout of forceful engagement with the brake disk stack for applying andreleasing braking force. The EMA may be mounted to a surface of thebrake head that is parallel to a friction surface of the brake diskstack.

In various embodiments, an EMA may be coupled to or otherwise operate aforce generating device such as, for example, a ball screw, a ram,and/or the like. In operation, the EMA may cause the force generatingdevice to move and/or exert a force on other brake system structure suchas, for example, a brake disk or pad to exert a stopping force on awheel or other suitable moving structure. This stopping force may loadand/or exert a corresponding force on the EMA structures such as, forexample, an EMA housing. This load may also be measured by measuringstrain to determine the amount of braking force being applied when thebrake system is activated.

In various embodiments and with reference to FIG. 1, a cross-sectionalschematic view of a conventional EMA 100 is shown. The EMA 100 maycomprise an EMA housing 110, an actuator drive unit (“ADU”) housing 130,a ball nut 125, a ball screw 120, and a disc or “puck” 105. The EMAhousing 100 may comprise a generally annular structure configured tohouse the ball nut 125 and extend along the axis A-A′. The ball nut 125may comprise a generally annular housing that extends axially along theaxis A-A′ within the EMA housing 110. The ball screw 120 may comprise agenerally annular housing that extends axially along the axis A-A′within the ball nut 125. The ADU housing 130 may comprise a generallyannular housing that extends axially along the axis A-A′ at leastpartially radially inward of the ball screw 120. An inner surface of theball nut 125 may be helically threaded. Likewise, an outer surface ofthe ball screw 120 may be helically threaded. As described above, theball screw 120 may be housed within the ball nut 125 and the threadingon the outer surface of the ball screw 120 may interface with or matewith the threading on the inner surface of the ball nut 125. A varietyof discrete components may be coupled to the ADU housing 130 within theEMA 100, such as, for example, thrust bearing 140, a load cell 170, ringgear and/or gearing system, and the like.

A portion of the EMA 100 is assembled from the following mainsub-systems that exist as separate components: The motor (ADU) housing130 is fitted with a planetary ring gear, which is then secured withmultiple roll pins that are inserted through the ADU housing 130 intothe ring gear body. These pins are the primary means of torque transferbetween the ring gear and the ADU housing 130. The EMA assembly 100 isthen completed by adding additional components (e.g. motor andresolver). The (roller) thrust bearing 140 is fitted to the ball screw120 and subsequently secured by welding (e.g. via Laser, EBM, etc.). Thethrust bearing 140 comprises rolling elements, a main bearing race, amain bearing cage, a preload ball bearing assembly and a preload spring.These are assembled as separate items. The load cell 170 is then fittedinto the EMA housing 110. Ball screw 120 and ADU housing 130 aresubsequently added and secured to the EMA 100 with the retention nut.

During operation, the ball screw 120 may rotate about an axis A-A′. Asthe ball screw 120 rotates, the threading in the ball screw 120 maycooperate with the threading in the ball nut 125 to drive the ball nut125 in a distal direction. As the ball nut 125 translates distally, thepuck coupled to the ball nut 125 may also translate distally. The puckmay contact a brake stack (e.g., of an aircraft wheel) to apply force tothe brake stack configured to apply a clamping force on a wheel therebyslowing and/or halting the rolling motion of the aircraft wheel.

In various embodiments and with reference to FIG. 2 an integrated ADUassembly 200 is depicted. Integrated ADU assembly 200 is configured toreceive a motor and resolver to the ADU housing 210. Integrated ADUassembly 200 may comprise at least one of an integrally formed ring gear230, an integrally formed thrust bearing 240 and integrally formed loadcell 270.

The ring gear 230 comprises a portion of a planetary gear pack generallydisposed annularly around the interior of ADU housing 210 near an openend proximate to end B′ of axis B-B′. The planetary ring gear 230 may bemachined into the ADU housing 210 to obtain reactionary support and apart count reduction (and cost reduction) in the EMA 300 (see FIG. 3).In association with a planetary gear transmission, the ring gear 230 isconfigured to translate the reactionary load of the planet gears thatrotate in the ring gear. A planetary gear system increases the torquefrom the motor to generate the load on the ball nut 225. The teeth 250of the ring gear 230 may be integrally formed in the interior diameterof the ADU housing 210. In this way, the pins which were historicallyused, such as in EMA 100, as the primary means of torque transferbetween the ring gear and the ADU housing 130 are eliminated. EMA 300may be more reliable as historical ring gear retaining pins have beenknown to break loose allowing the ring gear to rotate in the ADU housing110 thereby preventing the application of full load. This failure modeis eliminated in the design of integrated ADU assembly 200.

The thrust bearing assembly of integrated ADU assembly 200 is formed byinserting thrust bearing balls into the thrust bearing races 245(stationary race) between ADU housing 210 and ball screw 220 (with briefreference to FIG. 3). Ball nut 225 may communicate with ball screw 220via a bearing race 227. The integrated ADU assembly 200 to ball screw220 is assembled by insertion of ball bearings. This assembly is thensecured to the EMA housing 290, such as via the use of a retention nut.

With renewed reference to FIG. 2, integrated ADU assembly 200 maycomprise an integral load cell 270. The integrated load cell may be anydesired shape. According to various embodiments, ADU housing 210comprises a plurality of columns 280, such as four generally equallyspaced columns. Columns 280 may be formed through the incorporation ofopen areas 295 defined by a perimeter 290 located between two annularlyspaced apart adjacent columns 280 in load cell 270. These open areas 295may be configured to direct the force through the load cell 270. Statedanother way, columns 280 may be configured to funnel the compressiveloads of integrated ADU assembly 200 directly through the load cell 270strain gauge 277. Strain gauge 277 may be configured to measure load inany suitable direction relative to axis B-B′. For instance, strain gauge277 may be configured to measure at least one of a linear load and abending load on ADU housing 210. In this way, the design geometry of thecolumns 280 can be altered, designed and controlled to affect the gainoutput of the load cell 270 function. Load cell 270 may comprise atleast one sensor, such as a strain gauge 277, mounted within/on aportion of load cell 270, such as on/within column 280. These straingauges may be located at any location along the surface ADU housing 210,such as approximately 90° and/or approximately 180° apart about theannular surface of the ADU housing 210. The strain gauges 277 may beflush mounted through the use of a recess 275 formed in the column 280configured to receive the stain gauge 277. Wiring channels 285 coupledto the recess 275 may assist with the orienting of wired electricalconnections. ADU housing 210 having installed strain gauges 277 wired toa power source and/or controller may form the load cell 270.

Load cell 270 strain gauge 277 can be electrically coupled to othersystems, such as a power source and/or controller as wires may be routedthrough columns 280 and/or wiring channels 285 simplifying the wiringconnections during the EMA 300 assembly process. A flex circuit boardmay be utilized to reduce manufacturing costs (versus hand wiring thestrain gauges).

In various embodiments, strain gauges 277 may be installed on/in ADUhousing 210 and/or recess 275 in any suitable fashion. For example, abonding film such as a polyimide film (e.g., M PLY-001 KAPTON film fromE. I. du Pont de Nemours and Company) may be installed on ADU housing210 at a suitable location for strain gauge 277 installation. Morespecifically, the bonding film may be installed at each desired straingauge 277 location. The bonding film may be added for environmentaland/or electrical protection.

In various embodiments, at least portions of strain gauges 277, wires,and wiring recess 275 may be covered by a coating, tape, protectantand/or the like to protect the strain gauges 277, wires, and wiringterminals from environmental exposure (e.g., temperature, contaminants,and/or the like). In this regard, at least portions of strain gauges277, wires, and wiring terminals may be covered by a tape such as, forexample, a high temperature tape. At least portions of the strain gauges277, wires, and wiring terminals may also be coated and/or sealed with asuitable sealer such as silicon.

The integration of the thrust bearing races 245, which are locatednearer end B′ of axis B-B′ as compared with the columns 280 of load cell270, provide a direct path of the load through the columns 280 and thusthe strain gauge 277 thereby provide measurement of transmitted loads.The integration of the load cell 270 increases strain gauge 277measurement accuracy since the load cell 270 no longer has thecapability to move relative to the integrated ADU assembly 200 due tovibration, shock, and/or the like. It is known that these relativemovements between the load cell 270 and the thrust bearing 240 andhousing 210 can lead to load cell 270 measurement errors (e.g.measurements can drift high or low). Prior art load cells, such as loadcell 170, were typically installed as separate components inside theactuator housing, such as actuator housing 110, at the bottom end (e.g.end located nearest end A of axis A-A′) of the housing. These prior loadcells 170 may be susceptible to calibration and zero shifts of loadmeasurements because the load path of the prior load cells 170 varieddue to deflection, edge loading, and movement of the load cell 170within the actuator housing 110.

Integrated ADU assembly 200 is configured to enable increased powerdensity. Integrated ADU assembly 200 is configured to result in a weightand package size (e.g. EMA 300 size) reduction beneficial in aircraftbrake applications. In various embodiments, the present disclosureprovides an EMA 300 with weight and space savings. Moreover, EMA 300significantly reduces manufacturing and/or instrumentation time. Invarious embodiments, the systems and elements described herein mayprovide overall cost savings as compared to prior load cell systems.

In operation, utilizing integrated ADU assembly 200, load is transferredthrough the EMA as follows: puck (not shown), end-cap (not shown), ballnut, ball screw, thrust bearing (rotating race) to the ADU housing thatcontains the thrust bearing (stationary race), then through the integralcolumns that house the strain gauges that measure the applied load.Relative movement between the load cell 270 and the thrust bearing 240is eliminated and is also easier to control between the load cell 270and the EMA housing 290.

In various embodiments, while the integrated ADU assembly 200 describedherein has been described in the context of aircraft applications, onewill appreciate in light of the present disclosure, that the integralhousing load cells described herein may be used on various othervehicles such as, for example, trains. Moreover, the integral housingload cells described herein may be employed with any suitable electricmotor actuator in any installation. Thus, in various embodiments, theintegral housing load cells described herein provide a cost effectiveand reliable electric motor actuator.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the inventions. The scope of the inventions is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”, “anexample embodiment”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f), unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. An electric motor actuator comprising: anelectric motor actuator housing; a ball nut coupled to the electricmotor actuator housing; a ball screw in communication with the ball nutvia a race; and an actuator drive unit housing coupled to the ball screwto form a thrust bearing, wherein the actuator drive unit housingcomprises an integrally formed ring gear, an integrally formed thrustbearing race, and an integrally formed load cell, wherein the actuatordrive unit housing forms a column of the integrally formed load cell. 2.The electric motor actuator of claim 1, wherein the integrally formedload cell comprises a plurality of columns defined by openings betweenadjacent columns.
 3. The electric motor actuator of claim 2, wherein atleast one of the plurality of columns is configured to orient thedirection of force through the integrally formed load cell.
 4. Theelectric motor actuator of claim 1, wherein the integrally formed loadcell comprises a channel configured to route a sensor wire.
 5. Theelectric motor actuator of claim 1, wherein the column of the integrallyformed load cell defines a recess, and wherein a strain gauge isdisposed within the recess.
 6. The electric motor actuator of claim 1,further comprising a sensor flush mounted on the actuator drive unithousing within a recess.
 7. The electric motor actuator of claim 1,wherein teeth of the integrally formed ring gear are formed in aninterior surface of the actuator drive unit housing.